feat: add Cloudflare AI TTS engine (aura-2-en) with voice grouping in UI

backend/internal/runner/runner.go

@@ -27,6 +27,7 @@ import (
 	"go.opentelemetry.io/otel/codes"
 
 	"github.com/libnovel/backend/internal/bookstore"
+	"github.com/libnovel/backend/internal/cfai"
 	"github.com/libnovel/backend/internal/domain"
 	"github.com/libnovel/backend/internal/kokoro"
 	"github.com/libnovel/backend/internal/libretranslate"
@@ -112,6 +113,9 @@ type Dependencies struct {
 	// PocketTTS is the pocket-tts client (CPU, kyutai voices: alba, marius, etc.).
 	// If nil, pocket-tts voice tasks will fail with a clear error.
 	PocketTTS pockettts.Client
+	// CFAI is the Cloudflare Workers AI TTS client (cfai:* prefixed voices).
+	// If nil, CF AI voice tasks will fail with a clear error.
+	CFAI cfai.Client
 	// LibreTranslate is the machine translation client.
 	// If nil, translation tasks will fail with a clear error.
 	LibreTranslate libretranslate.Client
@@ -555,6 +559,18 @@ func (r *Runner) runAudioTask(ctx context.Context, task domain.AudioTask) {
 			return
 		}
 		log.Info("runner: audio generated via pocket-tts", "voice", task.Voice)
+	} else if cfai.IsCFAIVoice(task.Voice) {
+		if r.deps.CFAI == nil {
+			fail("cloudflare AI client not configured (CFAI_ACCOUNT_ID/CFAI_API_TOKEN empty)")
+			return
+		}
+		var genErr error
+		audioData, genErr = r.deps.CFAI.GenerateAudio(ctx, text, task.Voice)
+		if genErr != nil {
+			fail(fmt.Sprintf("cfai generate: %v", genErr))
+			return
+		}
+		log.Info("runner: audio generated via cloudflare AI", "voice", task.Voice)
 	} else {
 		if r.deps.Kokoro == nil {
 			fail("kokoro client not configured (KOKORO_URL is empty)")